This invention relates to conveyors, and more particularly to a system for tensioning a conveyor belt.
A conveyor typically includes a frame, a pair of rollers rotatably mounted to the frame, and a belt trained about the rollers such that rotatably driving one of the rollers results in driving of the belt and thereby rotation of the other roller. The belt must be tensioned in order to provide positive engagement with the rollers to insure proper operation of the conveyor.
Various mechanisms are known in the prior art to tension a conveyor belt by adjusting the spacing between the rollers. One such mechanism is disclosed in Dorner et al U.S. Pat. No. 5,174,435 issued Dec. 29, 1992, and assigned to the same assignee as the present application. In this patent, one of the rollers is mounted to a pair of plates, each of which is slidably mounted to one side of the frame. Each plate is interconnected with an extension mechanism which includes a pair of gear racks located one adjacent each side of the conveyor frame. An elongated drive pinion is engaged with each gear rack and is rotatably mounted to the frame, such that rotation of the pinion is translated through the gear racks to the plates for adjusting the position of one roller relative to the other and to thereby control the belt tension. A locking mechanism selectively locks the plates to the frame for preventing movement of the plates when the roller is in a desired position, and a tracking mechanism provides adjustment of the roller position to ensure proper belt tracking.
The above-described belt tensioning mechanism is highly satisfactory and provides reliable and positive belt tensioning throughout a wide range of positions. However, the system involves a number of components which are mounted to the frame and the adjustment plates, all of which involve an associated manufacturing cost.
It is an object of the present invention to provide a low cost system for tensioning a conveyor belt. It is a further object of the invention to provide a belt tensioning system which is simple in its components and which is easily operable by a user. Yet another object of the invention is to provide a conveyor belt tensioning mechanism utilizing a specially designed tool, separate from both the conveyor frame and the tensioning plates, which is manually operable by a user to tension the belt.
The invention contemplates a belt tensioning system for a conveyor having a frame, a conveying member such as a belt, at least one roller, and at least one movable tensioning member mounted to the frame and to which the roller is rotatably mounted. The tensioning member is movable between an extended, tensioned position in which the belt is tensioned, and a retracted, release position for introducing slack into the belt. The belt tensioning system of the invention is in the form of a manually operable tensioning device, separate from both the frame and the tensioning plate, which is selectively engageable with and disengageable from the frame. The tensioning device is movable when engaged with the frame into engagement with the tensioning plate, for moving the tensioning plate to its tensioned position. A locking mechanism is operable to maintain the tensioning plate in its tensioned position, such that the tensioning device can be disengaged from the frame and the locking mechanism functions to thereafter maintain the tensioning plate in its tensioned position. In a preferred form, the tensioning plate is slidably mounted to the frame for movement between its tensioned and release positions. Engagement of the locking mechanism functions to frictionally engage the tensioning plate with the frame to prevent sliding movement of the tensioning plate relative to the frame. The manually operable tensioning device is preferably in the form of a tool having a handle, a cam surface spaced from the handle, and a pivotable mounting arrangement for pivotably mounting the tool to the frame. Pivoting movement of the tool relative to the frame engages the cam surface of the tool with the tensioning plate, to slide the tensioning plate to its tensioned position. The pivotable mounting arrangement for pivotably mounting the tool to the frame preferably includes a recess formed in the frame and a pin associated with the mounting tool which is received within the recess, such that the tool is pivotable relative to the frame about a pivot axis defined by the pin. The tensioning plate includes an engagement surface with which the cam surface of the tool is engaged for moving the tensioning plate to its tensioned position upon pivoting movement of the tool, and the tool includes a retainer surface engaged with the tensioning plate engagement surface when the tool is pivoted to a predetermined position relative to the frame to place the tensioning plate in its tensioned position, and engagement of the tool retainer surface with the plate engagement surface functions to maintain the tensioning plate in its tensioned position.
In a preferred form, the conveyor has a pair of tensioning plates mounted one to each side of the frame on opposite sides of the belt, and the roller is rotatably mounted to and extends between the pair of tensioning plates. A pair of manually operable tensioning devices, each of which is preferably in the form of a tool as set forth above, are movable to place both of the tensioning plates in their extended, tensioned positions. In a preferred form, the tensioning tools are synchronously movable to place the tensioning devices in their tensioned positions. In one form, a rod or shaft member is positioned within aligned openings in the handle members of the tools to span between the tools, and the portion of the rod spanning between the tools is manually engaged by the user to pivot the tools relative to the frame to synchronously move the tensioning plates to their tensioned positions.
The invention further contemplates a method of tensioning a conveyor belt in a conveyor mechanism, substantially in accordance with the foregoing summary.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.